Semiconductor light emitting devices including patternable films comprising transparent silicone and phosphor, and methods of manufacturing same

ABSTRACT

Semiconductor light emitting devices include a semiconductor light emitting element having a light emitting surface, and a patternable film including transparent silicone and phosphor on at least a portion of the light emitting surface. The patternable film may be a photopatternable film and/or a printable film including transparent silicone and phosphor. The patternable film includes an aperture therein that exposes a portion of a light emitting surface, and a bond pad is provided on the light emitting surface in the aperture. A wire bond may be provided on the bond pad. Related methods of fabricating semiconductor light emitting devices are also provided.

FIELD OF THE INVENTION

This invention relates to microelectronic devices and fabricationmethods therefor, and more particularly to semiconductor light emittingdevices and fabrication methods therefor.

BACKGROUND OF THE INVENTION

Semiconductor light emitting devices, such as Light Emitting Diodes(LEDs) or laser diodes, are widely used for many applications. As iswell known to those having skill in the art, a semiconductor lightemitting device includes a semiconductor light emitting element havingone or more semiconductor layers that are configured to emit coherentand/or incoherent light upon energization thereof. It is also known thata semiconductor light emitting device generally is packaged to provideexternal electrical connections, heat sinking, lenses or waveguides,environmental protection and/or other functions.

Continued developments in LEDs have resulted in highly efficient andmechanically robust light sources that can cover the visible spectrumand beyond. These attributes, coupled with the potentially long servicelife of solid state devices, may enable a variety of new displayapplications, and may place LEDs in a position to compete with the wellentrenched incandescent and fluorescent lamps.

It may be desirable to provide a phosphor for an LED, for example toprovide solid-state lighting. In one example, LEDs that are used forsolid-state white lighting may produce high radiant flux output at shortwavelengths, for example in the range of about 380 nm to about 480 nm.One or more phosphors may be provided, wherein the short wavelength,high energy photon output of the LED is used to excite the phosphor, inpart or entirely, to thereby down-convert in frequency some or all ofthe LED's output to create the appearance of white light.

As one specific example, ultraviolet output from an LED at about 390 nmmay be used in conjunction with red, green and blue phosphors, to createthe appearance of white light. As another specific example, blue lightoutput at about 470 nm from an LED may be used to excite a yellowphosphor, to create the appearance of white light by transmitting someof the 470 nm blue output along with some secondary yellow emissionoccurring when part of the LEDs output is absorbed by the phosphor.

As is well known to those having skill in the art, at least twotechniques may be used to incorporate phosphor material into a lightemission path of an LED. In one technique, the phosphor may be suspendedin the packaging and/or encapsulation that is provided with the LED, sothat the phosphor is maintained in proximity to the LED. In analternative approach, the phosphor material is coated on the LED itself.When coating a phosphor, a liquid binder, such as an epoxy, may be used,in which one or more phosphors is suspended. The phosphor-containingbinder may be dispensed onto the LED prior to dispensing and curing aclear encapsulation epoxy. LEDs that employ phosphor coatings aredescribed, for example, in U.S. Pat. Nos. 6,252,254; 6,069,440;5,858,278; 5,813,753; and 5,277,840. Moreover, published U.S. patentapplication No. US 2004/0056260 A1, published on Mar. 25, 2004, entitledPhosphor-Coated Light Emitting Diodes Including Tapered Sidewalls, andFabrication Methods Therefor, the disclosure of which is herebyincorporated herein by reference in its entirety as if set forth fullyherein, describes a light emitting diode that includes a substratehaving first and second opposing faces and a sidewall between the firstand second opposing faces that extends at an oblique angle from thesecond face towards the first face. A conformal phosphor layer isprovided on the oblique sidewall. The oblique sidewall can allow moreuniform phosphor coatings than conventional orthogonal sidewalls.

SUMMARY OF THE INVENTION

Semiconductor light emitting devices according to embodiments of thepresent invention include a semiconductor light emitting element thatincludes a light emitting surface, and a patternable film comprisingtransparent silicone and phosphor on at least a portion of the lightemitting surface. The patternable film comprising transparent siliconeand phosphor may be a photopatternable film and/or a printable filmcomprising transparent silicone and phosphor. In some embodiments, thepatternable film comprising transparent silicone and phosphor includesan aperture therein that exposes a light emitting surface, and a bondpad is provided on the light emitting surface in the aperture. In otherembodiments, a wire bond is provided on the bond pad opposite the lightemitting surface.

In still other embodiments, the light emitting surface includes a faceand a sidewall that extends from the face, and the patternable filmcomprising transparent silicone and phosphor is on at least a portion ofthe face and on at least a portion of the sidewall. Moreover, in someembodiments, the patternable film comprising transparent silicone andphosphor is thicker, and in some embodiments at least 10% thicker, on atleast a portion of the sidewall than on at least a portion of the face.

In yet other embodiments, the phosphor is configured to convert at leastsome light that is emitted from the light emitting surface, such thatlight that emerges from the semiconductor light emitting device appearsas white light. In other embodiments, a patternable film comprisingtransparent silicone and free of phosphor is provided between the lightemitting surface and the transparent patternable film comprisingsilicone and phosphor.

In yet other embodiments of the present invention, a secondsemiconductor light emitting element is monolithically integrated with afirst semiconductor light emitting element, and the patternable filmcomprising transparent silicone and phosphor is provided on at least aportion of the light emitting surfaces of both the first and secondmonolithically integrated semiconductor light emitting elements. Instill other embodiments, first and second semiconductor light emittingelements are provided on a mounting tape and spaced apart from oneanother, and the patternable film comprising transparent silicone andphosphor is provided on at least a portion of the light emittingsurfaces of both the first and second semiconductor light emittingelements. In other embodiments, the patternable film comprisingtransparent silicone and phosphor also extends onto the mounting tapebetween the spaced apart first and second light emitting devices. Instill other embodiments, the light emitting surfaces include sidewallsfacing one another, and the patternable film comprising transparentsilicone and phosphor extends onto at least a portion of the face andsidewalls.

In still other embodiments of the present invention, multiple layers ofpatternable films comprising transparent silicone and phosphor may beprovided on at least a portion of the light emitting surface. In someembodiments, the phosphors in the various layers may be the same.However, in other embodiments, a first phosphor may be provided in afirst film and a second phosphor may be provided in a second film. Forexample, the first phosphor may be a green phosphor, and the secondphosphor may be a red phosphor. Yet other combinations of two or morepatternable films also may be provided.

Semiconductor light emitting devices may be fabricated, according tovarious embodiments of the present invention, by coating a patternablefilm comprising transparent silicone and phosphor on at least a portionof a light emitting surface of a semiconductor light emitting element.In some embodiments, a photopatternable film comprising transparentsilicone and phosphor is coated on at least a portion of the lightemitting surface of a semiconductor light emitting diode. In otherembodiments, a printable film comprising transparent silicone andphosphor is printed on at least a portion of a light emitting surface ofa semiconductor light emitting element. In some embodiments, thephotopatternable film comprising transparent silicone and phosphor isphotopatterned to form an aperture therein that exposes a light emittingsurface. In other embodiments, the printable film comprising transparentsilicone and phosphor is printed on at least a portion of the lightemitting surface of the semiconductor light emitting element, to definean aperture therein that exposes the light emitting surface. In yetother embodiments, a bond pad is formed on the light emitting surface ofthe aperture, and, in still other embodiments, a wire is bonded to thebond pad opposite the light emitting surface.

In some embodiments, coating is performed such that the patternable filmcomprising transparent silicone and phosphor is coated on at least aportion of the face of the light emitting surface and on at least aportion of a sidewall thereof. In some embodiments the coating isthicker, and, in some embodiments, at least 10% thicker, on at least aportion of the sidewall than on at least a portion of the face.

In some embodiments of the invention, photopatterning is performed byselectively exposing the photopatternable film comprising transparentsilicone and phosphor to define the aperture, and then developing thephotopatternable film comprising transparent silicone and phosphor thathas been exposed, to form the aperture. In still other embodiments, thephotopatternable film comprising transparent silicone and phosphor isagain developed to enlarge the aperture. In yet other embodiments, lightemission of a light emitting device is measured after developing thephotopatternable film comprising transparent silicone, and phosphor anda second development is performed if the light emission of the lightemitting device that is measured does not conform to at least onepredefined parameter, such as an emission frequency spectrum. In stillother embodiments, a photopatternable film comprising transparentsilicone and free of phosphor may be coated on at least a portion of thelight emitting surface prior to coating the photopatternable filmcomprising transparent silicone and phosphor.

Method embodiments of the present invention also may be used to coatmultiple semiconductor light emitting elements. In some embodiments, thepatternable film comprising transparent silicone and phosphor is coatedon at least a portion of multiple semiconductor light emitting elementsthat are monolithically integrated. In other embodiments a plurality ofsemiconductor light emitting devices are mounted on a mounting tape, andthe multiple semiconductor light emitting devices on a mounting tape arethen coated. In still other embodiments, the mounting tape is stretchedprior to coating to define spaces between adjacent devices, and thencoating is performed on the devices and on the spaces therebetween. Inyet other embodiments, sidewalls of the devices also are coated.

Yet other method embodiments of the present invention may coat more thanone patternable film comprising transparent silicon and phosphor on atleast a portion of the light emitting surface. In particular, in someembodiments, a patternable film comprising transparent silicone and afirst phosphor is first coated on the light emitting surface. Then, asecond patternable film comprising transparent silicone and a secondphosphor is coated on the first patternable film comprising transparentsilicone and a first phosphor. In some embodiments, the first phosphoris a green phosphor and the second phosphor is a red phosphor. Yet othercombinations of two or more patternable films also may be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 are cross-sectional views of semiconductor light emittingdevices according to various embodiments of the present invention.

FIGS. 7-9 are flowcharts illustrating manufacturing methods forsemiconductor light emitting devices according to various embodiments ofthe present invention.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. However, this invention should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. In the drawings, the thickness of layers and regions areexaggerated for clarity. Like numbers refer to like elements throughout.As used herein the term “and/or” includes any and all combinations ofone or more of the associated listed items.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

It will be understood that when an element such as a layer or region isreferred to as being “on” or extending “onto” another element, it can bedirectly on or extend directly onto the other element or interveningelements may also be present. In contrast, when an element is referredto as being “directly on” or extending “directly onto” another element,there are no intervening elements present. It will also be understoodthat when an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. In contrast, when anelement is referred to as being “directly connected” or “directlycoupled” to another element, there are no intervening elements present.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Furthermore, relative terms, such as “lower”, “base”, or “horizontal”,and “upper”, “top”, or “vertical” may be used herein to describe oneelement's relationship to another element as illustrated in the Figures.It will be understood that relative terms are intended to encompassdifferent orientations of the device in addition to the orientationdepicted in the Figures. For example, if the device in the Figures isturned over, elements described as being on the “lower” side of otherelements would then be oriented on “upper” sides of the other elements.The exemplary term “lower”, can therefore, encompasses both anorientation of “lower” and “upper,” depending of the particularorientation of the figure. Similarly, if the device in one of thefigures is turned over, elements described as “below” or “beneath” otherelements would then be oriented “above” the other elements. Theexemplary terms “below” or “beneath” can, therefore, encompass both anorientation of above and below.

Embodiments of the present invention are described herein with referenceto cross section illustrations that are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles that are illustrated, typically, may be rounded. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the precise shape of a region andare not intended to limit the scope of the present invention. Moreover,terms such as “horizontal”, “vertical” and “perpendicular” indicategeneral directions or relationships rather than precise 0° or 90°orientations.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 1 is a cross-sectional view of a semiconductor light emittingdevice according to various embodiments of the present invention.Referring now to FIG. 1, a semiconductor light emitting device 100according to various embodiments of the present invention includes asemiconductor light emitting element 110 that includes a light emittingsurface 110 a. A patternable film comprising transparent silicone andphosphor 120 is provided on at least a portion of the light emittingsurface 110 a. As used herein, “light” refers to any radiation, visibleand/or invisible (such as ultraviolet) that is emitted by asemiconductor light emitting element 110. Moreover, as used herein, theterm “transparent” means that at least some optical radiation thatenters the patternable film comprising transparent silicone and phosphor120 is emitted from the film 120.

Patternable films comprising transparent silicone are well known tothose having skill in the art. For example, Dow Corning® markets aseries of low stress patternable silicone materials, designated as DowCorning WL-3010 Printable Silicone and Dow Coming WL-5000 seriesPhotopatternable Spin-On Silicones. Dow Coming WL-3010 PrintableSilicone is a stencil-printable paste material designed to provide a lowstress, low-temperature-curable patterned silicone for a variety ofmicroelectronics applications. Although Dow Coming WL-3010 pastematerial is black, transparent paste also may be provided and/or thepaste may become transparent after curing. Dow Corning WL-5000 seriesPhotopatternable Spin-On Silicones include WL-5150, WL-5350 and WL-5351Photopatternable Spin-On Silicones, that are designed to provide lowstress, low temperature-curable transparent patterned films for avariety of micro- and optoelectronics applications. As noted in aproduct information brochure entitled “Information About Dow Corning®Brand Low-Stress Patternable Silicone Materials”, form no. 11-1108-01,copyright Dow Coming Corporation, 2003, these materials may havepotential uses such as high-volume wafer level or other integratedcircuit packaging applications; wafers, films, ceramics and laminates;stress-buffer layer applications; emerging applications using lead-freesolder; front and backside wafer protective layers; redistributionlayers; solder masks; negative photoresists; adhesive layers andsacrificial layers.

Phosphors also are well known to those having skill in the art. As usedherein, the phosphor may be Cerium-doped Yttrium Aluminum Garnet(YAG:Ce) and/or other conventional phosphors and may be mixed into apaste or solution of transparent patternable film comprising siliconeusing conventional mixing techniques, to thereby provide the transparentpatternable film comprising silicone and phosphor 120. In someembodiments, the phosphor is configured to convert at least some lightthat is emitted from the light emitting surface 110 a such that lightthat emerges from the semiconductor light emitting device 100 appears aswhite light.

The semiconductor light emitting element 110 may include a lightemitting diode, a laser diode and/or other semiconductor device thatincludes one or more semiconductor layers, which may include silicon,silicon carbide, gallium nitride and/or other semiconductor materials, asubstrate which may include sapphire, silicon, silicon carbide and/orother microelectronic substrates, and one or more contact layers, whichmay include metal and/or other conductive layers. In some embodiments,ultraviolet, blue and/or green LEDs may be provided. The design andfabrication of semiconductor light emitting devices are well known tothose having skill in the art and need not be described in detailherein.

For example, light emitting devices according to some embodiments of thepresent invention may include structures such as the galliumnitride-based LED and/or laser structures fabricated on a siliconcarbide substrate, such as those devices manufactured and sold by Cree,Inc. of Durham, N.C. The present invention may be suitable for use withLED and/or laser structures that provide active regions such asdescribed in U.S. Pat. Nos. 6,201,262; 6,187,606; 6,120,600; 5,912,477;5,739,554; 5,631,190; 5,604,135; 5,523,589; 5,416,342; 5,393,993;5,338,944; 5,210,051; 5,027,168; 5,027,168; 4,966,862 and/or 4,918,497,the disclosures of which are incorporated herein by reference in theirentirety as if set forth fully herein. Other suitable LED and/or laserstructures are described in published U.S. patent applicationPublication No. US 2003/0006418 A1 entitled Group III Nitride BasedLight Emitting Diode Structures With a Quantum Well and Superlattice,Group III Nitride Based Quantum Well Structures and Group III NitrideBased Superlattice Structures, published Jan. 9, 2003, as well aspublished U.S. patent application Publication No. US 2002/0123164 A1entitled Light Emitting Diodes Including Modifications for LightExtraction and Manufacturing Methods Therefor, the disclosures of whichare hereby incorporated herein by reference in their entirety as if setforth fully herein. Furthermore, phosphor coated LEDs, such as thosedescribed in U.S. application Ser. No. 10/659,241, entitledPhosphor-Coated Light Emitting Diodes Including Tapered Sidewalls andFabrication Methods Therefor, filed Sep. 9, 2003, the disclosure ofwhich is incorporated by reference herein as if set forth fully, mayalso be suitable for use in some embodiments of the present invention.The LEDs and/or lasers may be configured to operate such that lightemission occurs through the substrate. In such embodiments, thesubstrate may be patterned so as to enhance light output of the devicesas is described, for example, in the above-cited U.S. patent applicationPublication No. US 2002/0123164 A1.

FIG. 2 is a cross-sectional view of semiconductor light emitting devicesaccording to other embodiments of the present invention. As shown inFIG. 2, the patternable film comprising transparent silicone andphosphor 120 includes an aperture 122 therein that exposes a portion ofthe light emitting surface 110 a. When a photopatternable film is used,photolithography including exposure and development may be used todefine the aperture, as will be described in detail below. In contrast,when a printable film is used, screen or stencil printing may be used todefine the aperture while coating the printable film.

Still referring to FIG. 2, a bond pad 130 is provided on the lightemitting surface 110 a in the aperture 122. As also shown, in someembodiments of the present invention, a wire bond 140 is provided on thebond pad 130 opposite the light emitting surface 110 a. Bond pads andwire bonds are well known to those having skill in the art and need notbe described further herein. One example of bond pads and wire bonds isdescribed in application Ser. No. 10/899,793, filed Jul. 27, 2004,entitled Light Emitting Devices Having A Reflective Bond Pad And MethodsOf Fabricating Light Emitting Devices Having Reflective Bond Pads,assigned to the assignee of the present application, the disclosure ofwhich is hereby incorporated herein by reference in its entirety as ifset forth fully herein.

Accordingly, embodiments of the present invention can allow a phosphorto be coated on a semiconductor light emitting element prior tofabricating a bond pad and performing wire bonding. The patternable filmcomprising transparent silicone can be patterned using conventionalprinting or photolithographic techniques and can remain transparent evenwhen exposed to the relatively high temperatures, such as temperaturesof about 280° C. or more that are used to fabricate a bond pad andperform a wire bond. Thus, by coating a semiconductor light emittingelement with a patternable film comprising transparent silicone andphosphor according to some embodiments of the present invention, a layerof phosphor with a desired thickness and desired characteristics may beprovided on a semiconductor light emitting element prior to fabricatinga bond pad. This may allow the bond pad and wire bonding to take placewithout significantly degrading the operational characteristics of thesemiconductor light emitting device.

FIG. 3 is a cross-sectional view of semiconductor light emitting devicesaccording to other embodiments of the present invention. As shown inFIG. 3, the light emitting surface includes a face 110 b and at leastone sidewall 110 c that extends from the face 110 b. The patternablefilm comprising transparent silicone and phosphor 120 is on at least aportion of the face 110 b and on at least a portion of the sidewall 110c. Moreover, as also shown in FIG. 3, in some embodiments of the presentinvention, the patternable film comprising transparent silicone andphosphor 120 is thicker on at least a portion of the sidewall 110 c thanon at least a portion of the face 110 b. Thicker sidewall coatingsthereby may be provided.

In fact, in some embodiments, the patternable film comprising siliconeand phosphor is at least 10% thicker on at least a portion of thesidewall 110 c than on at least a portion of the face 110 b.Accordingly, some embodiments of the present invention can providephosphor-coated light emitting devices including tapered sidewalls,wherein the coating can be thicker on the sidewalls 110 c compared tothe face 110 b of the light emitting element. This may contrast sharplywith conventional light emitting devices, such as described in U.S. Pat.No. 6,642,652 to Collins III et al., in which variations in thickness ofa phosphor coating are less than or equal to 10% of the averagethickness. Heavily coated sidewall coatings thereby may be providedaccording to these embodiments of the present invention.

FIG. 4 is a cross-sectional view of semiconductor light emitting devicesaccording to yet other embodiments of the present invention. As shown inFIG. 4, a patternable film comprising transparent silicone and free ofphosphor 420 is provided between the light emitting surface 110 a andthe patternable film comprising transparent silicone and phosphor 120.In some embodiments, the film 420 may be provided by using any of theabove-described Dow Corning brand low stress patternable siliconematerials, without mixing phosphor therein. It will be understood,however, that other transparent patternable materials may be used andthat other materials may be mixed in film 420 to providelight-scattering and/or other properties. Moreover, the same transparentpatternable silicon material need not be used for films 120 and 420.

FIG. 5 is a cross-sectional view of semiconductor light emitting devicesaccording to other embodiments of the present invention. As shown inFIG. 5, a first semiconductor light emitting element 110 and a secondsemiconductor light emitting element 110′ are monolithically integrated,for example, by forming multiple semiconductor light emitting elementsin a wafer in a conventional manner. The first semiconductor lightemitting element 110 includes a first light emitting surface 110 a andthe second semiconductor light emitting element 110′ includes a secondlight emitting surface 110 a′. As shown in FIG. 5, the patternable filmcomprising transparent silicone and phosphor 120 is provided on at leasta portion of both the first and second light emitting surfaces 110 a,110 a′.

FIG. 6 is a cross-sectional view of semiconductor light emitting devicesaccording to yet other embodiments of the present invention. In FIG. 6,first and second semiconductor light emitting elements 110 and 110′ aremounted on a mounting tape 610. The mounting tape 610 may be aconventional “blue tape” that is conventionally used to hold dicedsemiconductor light emitting elements. As shown in FIG. 6, thepatternable film comprising transparent silicone and phosphor 120 is onat least a portion of the first and second light emitting surfaces 110 aand 110 a′, respectively. Moreover, as shown in FIG. 6, in someembodiments of the present invention, the first and second lightemitting elements 110 and 110′ are spaced apart from one another on themounting tape 610, for example, by stretching the mounting tape 610after the semiconductor light emitting elements 110, 110′ are mountedthereon, to define a space 620 therebetween. The photopatternable filmcomprising transparent silicone and phosphor 120 extends onto themounting tape 610 on the space 620 between the spaced apart first andsecond light emitting elements 110, 110′.

Moreover, as also shown in FIG. 6, in yet other embodiments, the firstlight emitting surface 110 a includes a first sidewall 110 c facing thesecond semiconductor light emitting element 110′, and the second lightemitting surface 110 a′ includes a second sidewall 110 c′ facing thefirst semiconductor light emitting element 110. The patternable filmcomprising transparent silicone and phosphor 120 extends onto at least aportion of the first and second sidewalls 110 c and 110 c′. Thus, afterdicing the individual light emitting devices 110, 110′ and stretchingthe mounting tape 610, some embodiments of FIG. 6 can produceembodiments of FIG. 3, where the coating 120 is thicker on the sidewalls110 c than on the face 110 b.

It will be understood by those having skill in the art that embodimentsof FIGS. 1-6 may be provided in various combinations and subcombinationsaccording to various other embodiments of the present invention.

Methods of fabricating semiconductor light emitting devices according tovarious embodiments of the present invention now will be described. Forexample, referring to FIGS. 1 and 7, a semiconductor light emittingdevice 100 may be fabricated by coating a patternable film comprisingtransparent silicone and phosphor 120 on at least a portion of a lightemitting surface 110 a of a semiconductor light emitting element 110, asshown at Block 710 of FIG. 7. In some embodiments of the invention,where the patternable film comprising transparent silicone and phosphor120 is a printable film comprising silicone and phosphor, coating atBlock 710 may be performed by stencil printing or screen printingequipment. Moreover, in embodiments of the invention where thepatternable film comprising transparent silicone and phosphor 120 is aphotopatternable film comprising silicone and phosphor, coating at Block710 may be performed by, for example, spin-coating the photopatternablefilm comprising transparent silicone and phosphor.

Referring again to Block 710, according to other embodiments of thepresent invention, prior to coating the patternable film comprisingtransparent silicone and phosphor 120 on at least a portion of the lightemitting surface of the semiconductor light emitting element at Block710, at least a portion of the light emitting surface may be coated witha patternable film comprising transparent silicone and free of phosphor,for example as shown at 420 of FIG. 4. Coating of Block 710 then may beperformed.

Referring to Block 720 of FIG. 7 and to FIG. 2, if transparentphotopatternable film is used, the photopatternable film comprisingtransparent silicone and phosphor 120 may be photopatterned to form anaperture 122 therein that exposes the light emitting surface 110 a. Whena printable film comprising transparent silicone and phosphor is used,the screen- or stencil-printing itself may be used to define theaperture 122, and photopatterning of Block 720 need not be performed. Itwill also be understood that if operations of Blocks 710 and 720 arebeing performed at the wafer level, these operations also may be used todefine and provide dicing streets for dicing the wafer.

Referring now to Block 730 of FIG. 7 and again to FIG. 2, a bond pad 130may be formed on the light emitting surface 110 a in the aperture 122.Finally, at Block 740, a wire bond 140 may be bonded to the bond pad 130opposite the light emitting surface 110 a.

Referring again to Block 710 of FIG. 7 and to FIGS. 3 and 6, coating maybe performed so as to coat the patternable film comprising transparentsilicone and phosphor 120 on at least a portion of the face 110 a, 1110a′ and on at least a portion of the sidewall 110 c, 110 c′. As shown,for example, in FIG. 6, these embodiments may provide a patternable filmcomprising transparent silicone and phosphor 120 that is thicker on atleast a portion of the sidewall 110 c, 110 c′, and, in some embodiments,at least 10% thicker, than on at least a portion of the face 110 a, 110a′.

FIG. 8 is a flowchart that illustrates operations for photopatterningaccording to various embodiments of the present invention, which maycorrespond to Block 720 of FIG. 7 when a transparent photopatternablefilm is used. In particular, referring to FIG. 8, at Block 810, thephotopatternable film comprising transparent silicone and phosphor 120is selectively exposed to define an aperture, such as the aperture 122of FIG. 2. Then, at Block 820, the photopatternable film comprisingtransparent silicone and phosphor, that has been exposed, is developed(rinsed) to form the aperture 122. Exposure and development may takeplace as described in the above-cited “Information About Dow Corning®Brand Low-Stress Patternable Silicone Materials”, or using otherconventional techniques. Referring again to FIG. 8, at Block 830, thelight emission of the light emitting device is measured and it isdetermined whether the light emitting device that is measured conformsto at least one predefined parameter, such as a desired emissionfrequency spectrum. If yes, photopatterning ends. If not, thephotopatternable film comprising transparent silicone and phosphor isagain developed (rinsed) at Block 820 to enlarge the aperture.

Embodiments of the present invention that include Block 830 may arisefrom a recognition that a single development step may not fully develop(wash away) unpatterned portions of the photopatternable film comprisingtransparent silicone and phosphor. Accordingly, if the light emissionspectrum is not satisfactory, a controlled additional amount of thefilm, including the phosphor therein, may be removed by performing asecond or subsequent development. Accordingly, individual semiconductorlight emitting devices may be “trimmed” to meet a desired opticalemission parameter.

Operations of FIGS. 7 and 8 may be performed on an individualsemiconductor light emitting device or on a plurality of semiconductorlight emitting devices, either prior to or after dicing. For example,embodiments of FIG. 5 may be fabricated according to embodiments ofBlock 710 of FIG. 7 by coating a patternable film comprising transparentsilicone and phosphor 120 on at least a portion of light emittingsurfaces of a plurality of semiconductor light emitting elements thatare monolithically integrated. Thus, in some embodiments, coating and/orother operations of FIG. 7 may be performed at the wafer stage prior todicing.

FIG. 9 is a flowchart of other operations that may be performed to coat,which may correspond to Block 710 of FIG. 7, according to otherembodiments of the present invention. These embodiments also maycorrespond to devices of FIG. 6.

In particular, referring to FIG. 9, at Block 910, a plurality ofsemiconductor light emitting devices are mounted on a mounting tape 610such as conventional “blue tape.” These devices may be singulateddevices from a wafer, or a wafer may be singulated after mounting on themounting tape 610. Optionally, as shown in Block 920, if it is desiredto thickly coat the sidewalls of the devices, the mounting tape 610 maybe stretched to space apart the devices. In other embodiments, thedevices may be placed on the mounting tape 610 in spaced apart relation.In yet other embodiments, the sidewalls may be coated without the needto space apart the devices.

Then, at Block 930, a patternable film comprising transparent siliconeand phosphor 120 is formed on at least a portion of the light emittingsurfaces 110 a, 110 a′ of the plurality of semiconductor light emittingelements 110, 110′ that are mounted on the mounting tape 610. In someembodiments of Block 930, the patternable film comprising transparentsilicone and phosphor 120 is also coated on the mounting tape 610 in thespaces 620 between adjacent semiconductor light emitting devices 110,110′, as shown in FIG. 6. Moreover, in yet other embodiments at least aportion of the sidewalls 110 c, 110 c′ are also coated with thephotopatternable film comprising 25 transparent silicone and phosphor120.

Embodiments of the present invention that were described above inconnection with FIGS. 1-9 have described a single patternable filmcomprising transparent silicone and phosphor. However, any of theseembodiments may also employ two or more patternable films comprisingtransparent silicone and phosphor. Thus, in some embodiments of thepresent invention, a first patternable film comprising transparentsilicone and a first phosphor is provided or coated on at least aportion of the light emitting surface of a semiconductor light emittingelement. A second patternable film comprising transparent silicone and asecond phosphor is then provided or coated on the first patternable filmcomprising transparent silicone and a first phosphor, opposite the lightemitting surface. Three or more layers of patternable film comprisingtransparent silicone and phosphor also may be provided.

The phosphors in two or more of these multiple layers may be identicalor may be different. Thus, for example, a blue semiconductor lightemitting device may be provided by providing a first patternable filmcomprising transparent silicone and green phosphor, and a secondpatternable film comprising transparent silicone and red phosphor on thefirst patternable film comprising transparent silicone and greenphosphor. In other embodiments, an ultraviolet semiconductor lightemitting element may be provided with separate patternable films thatcomprise transparent silicone and red, green and blue phosphors,respectively.

Moreover, in some embodiments, due to the competing absorption andemission processes, it may be desirable for the light emitting surfaceto excite the higher energy (emission) phosphors before the lower energy(emission) phosphors. Accordingly, in some embodiments of the presentinvention, a blue semiconductor light emitting element may be providedwith a first patternable film comprising transparent silicone and greenphosphor and a second patternable film comprising transparent siliconeand red phosphor, so that the blue light that is emitted from the lightemitting surface first interacts with the green phosphor and theninteracts with the red phosphor. Separate cure and develop processes maybe performed on an underlying patternable film prior to forming anoverlying patternable film. Alternatively, a common cure and developprocess may be performed.

Additional discussion of various embodiments of the present inventionnow will be provided. In particular, some embodiments of the presentinvention allow patternable films comprising transparent silicone to beused to add phosphor to a light emitting element. Photopatternablematerial can be patterned with ultraviolet light just like a photoresistmaterial and behaves as a negative patternable material where areas thatare not exposed are later washed away during development. Thus, if aphosphor such as YAG:Ce is mixed with a silicone material of this type,and the appropriate wavelength of UV light is selected, for example, toprovide low absorption of the phosphor and low reflection, the formationof a vertical LED structure with a blue LED and yellow coating canprovide a “white” LED. Additionally, multiple phosphors can be used forbetter color rendering. It will be understood that as used herein“vertical” means a general direction that is perpendicular to the face110 a, 110 a′ of a semiconductor light emitting element 110, 110′.

In some embodiments of the present invention, the coating includingphosphor on the semiconductor light emitting element can provide betterCorrelated Color Temperature (CCT) control and can allow packagers tomake white devices by using a white chip, as opposed to putting a globof phosphor in the package while packaging the chip.

Moreover, as was described above in connection with FIG. 8, thephotopatternable film comprising transparent silicone 120 may have poorselectivity when developing the pattern, in that some of the exposedregion may also wash off. This can be considered an additional desirablefeature in some embodiments of the invention. In particular, if too muchcoating is provided so that the desired optical property is notobtained, this poor selectivity may actually be used to erode awayadditional material to match the desired color point. This eroding awaymay be performed at the wafer level and/or at the die level. Moreover,as was described above, depending on the wafer/chip geometries, thecoating can be performed at the wafer level and/or after dicing on ablue tape.

Accordingly, some embodiments of the present invention can allow amanufacturer of a semiconductor light emitting device to open up thewire bond location while coating the rest of the light emitting wafer orchip, so that a vertical geometry may be used. The patternable materialalso may be used as a solder mask in that it fits the temperature limitsthat are desired for die attach. Also, due to the poor selectivity ofthe developing nature (i.e., erosion of the material that should not besoluble in the developer), this feature can be used to tune in the colorpoint.

Finally, as was described above, coating operations according toembodiments of the present invention may be performed at the waferlevel, at the wafer level after probing and testing and/or at thestretched tape level. At the wafer level, the wafer may be coated,initially cured, exposed and developed to open up bond pads, and,optionally, dicing streets. An optional final cure may then be performedfollowed by wafer probing, dicing, sorting and packaging. Moreover, if afinal cure has not been performed at the wafer level, the wafer may bediced, picked and tested, and material may be selectively removed toadjust the color point that was described in connection with FIG. 8. Afinal cure then may be performed at the die level followed by sortingand packaging. At the stretched tape level, a partial stretch may beperformed after dicing, after which coating, curing, exposure anddeveloping may be performed, followed by picking, testing and sorting aswas already described.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A semiconductor light emitting device comprising: a semiconductorlight emitting element that includes a light emitting surface; and apatternable film comprising transparent silicone and phosphor on atleast a portion of the light emitting surface.
 2. A semiconductor lightemitting device according to claim 1 wherein the patternable filmcomprising transparent silicone and phosphor includes an aperturetherein that exposes a portion of the light emitting surface, andwherein the semiconductor light emitting device further comprises a bondpad on the exposed portion of the light emitting surface in theaperture.
 3. A semiconductor light emitting device according to claim 2further comprising a wire bond on the bond pad opposite the lightemitting surface.
 4. A semiconductor light emitting device according toclaim 1 wherein the light emitting surface includes a face and asidewall that extends from the face, and wherein the patternable filmcomprising transparent silicone and phosphor is on at least a portion ofthe face and on at least a portion of the sidewall.
 5. A semiconductorlight emitting device according to claim 4 wherein the patternable filmcomprising transparent silicone and phosphor is thicker on the at leasta portion of the sidewall than on the at least a portion of the face. 6.A semiconductor light emitting device according to claim 5 wherein thepatternable film comprising transparent silicone and phosphor is atleast 10% thicker on the at least a portion of the sidewall than on theat least a portion of the face.
 7. A semiconductor light emitting deviceaccording to claim 1 wherein the phosphor is configured to convert atleast some light that is emitted from the light emitting surface suchthat light that emerges from the semiconductor light emitting deviceappears as white light.
 8. A semiconductor light emitting deviceaccording to claim 1 further comprising: a patternable film comprisingtransparent silicone and free of phosphor, between the light emittingsurface and the transparent patternable film comprising silicone andphosphor.
 9. A semiconductor light emitting device according to claim 1wherein the semiconductor light emitting element comprises a firstsemiconductor light emitting element and wherein the light emittingsurface comprises a first light emitting surface, the semiconductorlight emitting device further comprising: a second semiconductor lightemitting element that is monolithically integrated with the firstsemiconductor light emitting element and that includes a second lightemitting surface; and wherein the patternable film comprisingtransparent silicone and phosphor is on at least a portion of the firstand second light emitting surfaces.
 10. A semiconductor light emittingdevice according to claim 1 wherein the semiconductor light emittingelement comprises a first semiconductor light emitting element andwherein the light emitting surface comprises a first light emittingsurface, the semiconductor light emitting device further comprising: asecond semiconductor light emitting element that includes a second lightemitting surface; and a mounting tape; wherein the first and secondlight emitting devices are on the mounting tape and spaced apart fromone another; and wherein the patternable film comprising transparentsilicone and phosphor is on at least a portion of the first and secondlight emitting surfaces.
 11. A semiconductor light emitting deviceaccording to claim 10 wherein the patternable film comprisingtransparent silicone and phosphor extends onto the mounting tape betweenthe spaced apart first and second light emitting devices.
 12. Asemiconductor light emitting device according to claim 11 wherein thefirst light emitting surface includes a first sidewall facing the secondsemiconductor light emitting element, wherein the second light emittingsurface includes a second sidewall facing the first semiconductor lightemitting element and wherein the patternable film comprising transparentsilicone and phosphor also extends onto at least a portion of the firstand second sidewalls.
 13. A semiconductor light emitting deviceaccording to claim 1 wherein the patternable film comprising transparentsilicone and phosphor comprises a photopatternable film transparentcomprising silicone and phosphor.
 14. A semiconductor light emittingdevice according to claim 1 wherein the patternable film comprisingtransparent silicone and phosphor comprises a printable film comprisingtransparent silicone and phosphor.
 15. A semiconductor light emittingdevice according to claim 1 wherein the patternable film comprisingtransparent silicone and phosphor is a first patternable film comprisingtransparent silicone and a first phosphor, the device furthercomprising: a second patternable film comprising transparent siliconeand a second phosphor on the first patternable film comprisingtransparent silicone and a first phosphor, opposite the light emittingsurface.
 16. A semiconductor light emitting device according to claim 15wherein the first phosphor comprises a green phosphor and the secondphosphor comprises a red phosphor.
 17. A method of fabricating asemiconductor light emitting device comprising: coating a patternablefilm comprising transparent silicone and phosphor on at least a portionof a light emitting surface of a semiconductor light emitting element.18. A method according to claim 17 wherein coating comprises coating aphotopatternable film comprising transparent silicone and phosphor onthe at least a portion of a light emitting surface of a semiconductorlight emitting element.
 19. A method according to claim 17 whereincoating comprises printing a printable film comprising transparentsilicone and phosphor on the at least a portion of a light emittingsurface of a semiconductor light emitting element.
 20. A methodaccording to claim 18 further comprising: photopatterning thephotopatternable film comprising transparent silicone and phosphor toform an aperture therein that exposes a portion of the light emittingsurface.
 21. A method according to claim 19 further comprising: printingthe printable film comprising transparent silicone and phosphor on theat least a portion of a light emitting surface of a semiconductor lightemitting element to define an aperture therein that exposes a portion ofthe light emitting surface.
 22. A method according to claim 20 furthercomprising: forming a bond pad on the exposed portion of the lightemitting surface in the aperture.
 23. A method according to claim 21further comprising: forming a bond pad on the exposed portion of thelight emitting surface in the aperture.
 24. A method according to claim22 further comprising: bonding a wire to the bond pad opposite the lightemitting surface.
 25. A method according to claim 23 further comprising:bonding a wire to the bond pad opposite the light emitting surface. 26.A method according to claim 17 wherein the light emitting surfaceincludes a face and a sidewall that extends from the face, and whereincoating comprises coating the patternable film comprising transparentsilicone and phosphor on at least a portion of the face and on at leasta portion of the sidewall.
 27. A method according to claim 26 whereincoating comprises coating the patternable film comprising transparentsilicone and phosphor thicker on the at least a portion of the sidewallthan on the at least a portion of the face.
 28. A method according toclaim 27 wherein coating comprises coating the patternable filmcomprising transparent silicone and phosphor at least 10% thicker on theat least a portion of the sidewall than on the at least a portion of theface.
 29. A method according to claim 17 wherein the phosphor isconfigured to convert at least some light that is emitted from the lightemitting surface such that light that emerges from the semiconductorlight emitting device appears as white light.
 30. A method according toclaim 20 wherein photopatterning comprises: selectively exposing thephotopatternable film comprising transparent silicone and phosphor todefine the aperture; and developing the photopatternable film comprisingtransparent silicone and phosphor that has been exposed, to form theaperture.
 31. A method according to claim 30 further comprising: againdeveloping the photopatternable film comprising transparent silicone andphosphor that has been developed, to enlarge the aperture.
 32. A methodaccording to claim 31 wherein the following is performed betweendeveloping and again developing: measuring light emission of the lightemitting device; and wherein again developing is performed if the lightemission of the light emitting device that is measured does not conformto at least one predefined parameter.
 33. A method according to claim 32wherein the at least one predefined parameter comprises an emissionfrequency spectrum.
 34. A method according to claim 17 wherein coatingis preceded by: coating a patternable film comprising transparentsilicone and free of phosphor on at least a portion of the lightemitting surface.
 35. A method according to claim 17 wherein coatingcomprises: coating a transparent patternable film comprising siliconeand phosphor on at least a portion of light emitting surfaces of aplurality of semiconductor light emitting elements that aremonolithically integrated.
 36. A method according to claim 17 whereinthe patternable film comprising transparent silicone and phosphor is afirst patternable film comprising transparent silicone and a firstphosphor, the method further comprising: coating a second patternablefilm comprising transparent silicone and a second phosphor on the firstpatternable film comprising transparent silicone and a first phosphor.37. A method according to claim 36 wherein the first phosphor comprisesa green phosphor and the second phosphor comprises a red phosphor.
 38. Amethod according to claim 17: wherein coating is preceded by mounting aplurality of semiconductor light emitting devices includingcorresponding light emitting surfaces, on a mounting tape; and whereincoating comprises coating a patternable film comprising transparentsilicone and phosphor on at least a portion of the light emittingsurfaces of the plurality of semiconductor light emitting elements thatare mounted on the mounting tape.
 39. A method according to claim 38:wherein the following is performed between mounting and coating:stretching the mounting tape to define spaces between adjacentsemiconductor light emitting devices; and wherein coating comprisescoating a patternable film comprising transparent silicone and phosphoron at least a portion of the light emitting surfaces of the plurality ofsemiconductor light emitting elements that are mounted on the mountingtape and on the spaces between adjacent semiconductor light emittingdevices.
 40. A method according to claim 39 wherein the semiconductorlight emitting surfaces include sidewalls and wherein coating comprises:coating a patternable film comprising transparent silicone and phosphoron at least a portion of the light emitting surfaces of the plurality ofsemiconductor light emitting elements that are mounted on the mountingtape and on the spaces between adjacent semiconductor light emittingdevices so as to coat at least a portion of sidewalls of thesemiconductor light emitting elements with the patternable filmcomprising transparent silicone and phosphor.